.\" -*- nroff -*-
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" Copyright (c) 2011-2015 Cisco Systems, Inc.  All rights reserved.
.\" Copyright (c) 2020      Google, LLC. All rights reserved.
.\" $COPYRIGHT$
.TH MPI_Testsome 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
.SH NAME
\fBMPI_Testsome\fP \- Tests for completion of one or more previously initiated communications in a list.

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
int MPI_Testsome(int \fIincount\fP, MPI_Request \fIarray_of_requests[]\fP,
	int\fI *outcount\fP, int\fI array_of_indices[]\fP,
	MPI_Status\fI array_of_statuses[]\fP)

.fi
.SH Fortran Syntax
.nf
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TESTSOME(\fIINCOUNT, ARRAY_OF_REQUESTS, OUTCOUNT,
		ARRAY_OF_INDICES, ARRAY_OF_STATUSES, IERROR\fP)
	INTEGER	\fIINCOUNT, ARRAY_OF_REQUESTS(*)\fP
	INTEGER	\fIOUTCOUNT, ARRAY_OF_INDICES(*)\fP
	INTEGER	\fIARRAY_OF_STATUSES(MPI_STATUS_SIZE,*), IERROR\fP

.fi
.SH Fortran 2008 Syntax
.nf
USE mpi_f08
MPI_Testsome(\fIincount\fP, \fIarray_of_requests\fP, \fIoutcount\fP, \fIarray_of_indices\fP,
		\fIarray_of_statuses\fP, \fIierror\fP)
	INTEGER, INTENT(IN) :: \fIincount\fP
	TYPE(MPI_Request), INTENT(INOUT) :: \fIarray_of_requests(incount)\fP
	INTEGER, INTENT(OUT) :: \fIoutcount\fP, \fIarray_of_indices(*)\fP
	TYPE(MPI_Status) :: \fIarray_of_statuses(*)\fP
	INTEGER, OPTIONAL, INTENT(OUT) :: \fIierror\fP

.fi
.SH INPUT PARAMETERS
.ft R
.TP 1i
incount
Length of array_of_requests (integer).
.TP 1i
array_of_requests
Array of requests (array of handles).

.SH OUTPUT PARAMETERS
.ft R
.TP 1i
outcount
Number of completed requests (integer).
.TP 1i
array_of_indices
Array of indices of operations that completed (array of integers).
.TP 1i
array_of_statuses
Array of status objects for operations that completed (array of status).
.ft R
.TP 1i
IERROR
Fortran only: Error status (integer).

.SH DESCRIPTION
.ft R
Behaves like MPI_Waitsome, except that it returns immediately.
.sp
Returns in outcount the number of requests from the list
array_of_requests that have completed. Returns in the first outcount
locations of the array array_of_indices the indices of these
operations (index within the array array_of_requests; the array is
indexed from 0 in C and from 1 in Fortran). Returns in the first
outcount locations of the array array_of_status the status for these
completed operations. If a request that completed was allocated by a
nonblocking communication call, then it is deallocated, and the
associated handle is set to MPI_REQUEST_NULL.
.sp
If no operation has completed it returns outcount = 0. If there is no
active handle in the list, it returns outcount = MPI_UNDEFINED.
.sp
MPI_Testsome is a local operation, which returns immediately, whereas MPI_Waitsome blocks until a communication completes, if it was passed a list that contains at least one active handle. Both calls fulfill a fairness requirement: If a request for a receive repeatedly appears in a list of requests passed to MPI_Waitsome or MPI_Testsome, and a matching send has been posted, then the receive will eventually succeed unless the send is satisfied by another receive; send requests also fulfill this fairness requirement.
.sp
Errors that occur during the execution of MPI_Testsome are handled as for
MPI_Waitsome.
.sp
If your application does not need to examine the \fIarray_of_statuses\fP field, you can save resources by using the predefined constant MPI_STATUSES_IGNORE can be used as a special value for the \fIarray_of_statuses\fP argument.

.SH NOTES
The use of MPI_Testsome is likely to be more
efficient than the use of MPI_Testany. The former returns information on all completed communications; with the latter, a new call is required for each communication that completes.
.sp
A server with multiple clients can use MPI_Waitsome so as not to starve any client. Clients send messages to the server with service requests. The server calls MPI_Waitsome with one receive request for each client, then handles all receives that have completed. If a call to MPI_Waitany is used instead, then one client could starve while requests from another client always sneak in first.

.SH ERRORS
For each invocation of MPI_Testsome, if one or more requests generate
an MPI error, only the \fIfirst\fP MPI request that caused an
error will be passed to its corresponding error handler.  No other
error handlers will be invoked (even if multiple requests generated
errors).  However, \fIall\fP requests that generate an error
will have a relevant error code set in the corresponding
status.MPI_ERROR field (unless MPI_STATUSES_IGNORE was used).
.sp
The default error handler aborts the MPI job, except for I/O function
errors. The error handler may be changed with MPI_Comm_set_errhandler,
MPI_File_set_errhandler, or MPI_Win_set_errhandler (depending on the
type of MPI handle that generated the MPI request); the predefined
error handler MPI_ERRORS_RETURN may be used to cause error values to
be returned. Note that MPI does not guarantee that an MPI program can
continue past an error.
.sp
If the invoked error handler allows MPI_Testsome to return to the
caller, the value MPI_ERR_IN_STATUS will be returned in the C and
Fortran bindings.

.SH SEE ALSO
.ft R
.sp
MPI_Comm_set_errhandler
.br
MPI_File_set_errhandler
.br
MPI_Test
.br
MPI_Testall
.br
MPI_Testany
.br
MPI_Wait
.br
MPI_Waitall
.br
MPI_Waitany
.br
MPI_Waitsome
.br
MPI_Win_set_errhandler
.br

